Atactic or amorphous polypropylenes (APP), are known for their propensity for agglomeration, fouling, caking or, more simply, for their tackiness. This material was once in oversupply as it was the unwanted byproduct of isotactic polypropylene (IPP) production. During the past ten years, however, it has gained a considerable market as a principal component of modified bitumen one-ply roofing. Today the APP material most widely used by the roofing industry is the amorphous byproduct of isotactic polypropylene, which is a mixture of APP, IPP and amorphous ethylene/propylene copolymer and is herein referred to as byproduct polypropylene (BPP).
BPP is now becoming scarce since IPP catalysts used currently produce only negligible quantities of this byproduct. Suppliers of BPP are therefore turning their efforts towards production, as a staple commercial product, of APP and of materials similar in composition and physical characteristics to the BPP currently used by the roofing industry. U.S. Pat. No. 4,777,216 to V. Busico, for example, discloses a method for the synthesis of polymeric polyolefin alloy materials which have a consistent and reproducible composition similar to BPP. A major drawback in the industrial scale production of materials like APP is the difficulty created by their tackiness at the separation, discharge and packaging stages of the production process. As can be imagined, tacky materials tend to stick to process internal parts, such as vessel, pipe or valve walls, and to form agglomerates which present dangers of encrustment and clogging.